High speed drafting apparatus



jufiy 18, 1967 c. FIELD, JR 3,331,104

HIGH SPEED DRAFTING APPARATUS Filed Dec. 6, 1965 DRAFTING INTAKE 2m AFRO" morn ROLLS INVENTOR FREDERICK C. FIELD, JR.

ATTORNEY United States Patent 3,331,104 HIGH SPEED DRAFTING APPARATUS Frederick Cromwell Field, Jr., Wilmington, DeL, assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware Filed Dec. 6, 1965, Ser. No. 511,886 1 Claim. (Cl. 19-244) This invention relates to improvements in sliver drafting and more particularly to a novel system that permits high-speed drafting of staple fibers.

Drafting of sliver or roving is accomplished by passing a fiber bundle between two pairs of pinch rolls, the surface speed of the second pair or front rolls being considerably higher than that of the first pair or back rolls, and the distance between them being somewhat in excess of the maximum fiber length. Between these pairs of pinch rolls are usually found fiber control aprons between Which the fibers are made to pass. They are located as close to the input nip of the second pair of rolls as is practicable. These aprons normally move at a speed only slightly in excess of the first, slower speed pinch rolls. These aprons provide an even delivery to the nip of the second pair of pinch rolls. Under normal drafting conditions, the surface speed of the second or front pair of rolls is rarely if ever in excess of 30 yds./ min.

New high-speed textile spinning apparatus has created a need for greater output of drafted sliver. To satisfy this demand, attempts have been made to increase the speed of the front drafting rolls. Since the front drafting rolls are under load, an increase in speed generates excessive heat and causes rapid break-down of the roll bearings.

Air is entrained by the converging surfaces of the front drafting rolls and is directed toward the nip. These air currents are blocked by the nip, diverge and pass on either side of the roll. When the rolls are operated at high speeds, the air currents pick up fiber ends from the sliver in the gap between the drafting control sliver feed ing apron and the nip of the front rolls, and carry them out of their intended path. Loss of such fibers results in a nonuniform drafted product, and ultimately in poor quality yarn.

An object of this invention is to draft sliver at high speeds while maintaining adequate control of the fibers during the drafting process to produce a uniform prdouct. Other objects will be apparent from a description of the invention given below.

The present invention provides a novel process and apparatus arrangement for drafting sliver. Essentially, the novel drafting apparatus comprises a pair of loaded back rolls for metering the input of sliver and in sequence, drafting control aprons and a pair of loaded enlarged front rolls that are aproned with idler rolls. The latter are intake aprons, each passing over a front roll and an idler roll located between the front rolls and the drafting control aprons. In the process, a sliver is fed through the nip of a set of back rolls and in sequence therewith, through drafting control rolls equipped with aprons which feed the sliver directly into nip of a set of intake aprons, each intake apron passing over an idler roll and a front roll, the front rolls being under load to achieve the drafting. In this system, the diameter of the front rolls will ordinarily be between 1.3 and 3 times that of the back rolls, that is at least 30% greater than the diameter of the back rolls. In addition, the intake aprons in advance of the front rolls will normally be between 0.010 and 0.10 inch from the exit end of the drafting control aprons and the clearance between the idler rolls is generally between 0.005 and 0.03 inch. The set of idler rolls which are aproned to the front rolls are preferably 3,331,104 Patented July 18, 1967 made of steel containing suitable precision bearings for operating at high speeds. The high-speed operation of the idler rolls presents no real problem in view of the fact that compared to the front drafting rolls, they are under no load. One or more sets of drafting control aprons may be used in the drafting system.

The present invention will be more readily understood by reference to the accompanying drawing.

The drawing is a schematic representation of a standard sliver drafting system and includes the novel front roll drafting system of the present invention.

Referring to the drawing, a fiber bundle 3 is passed between two pairs of pinch rolls, 1, 1 and 2, 2 the surface speed of the second pair of front rolls, 2, 2' being considerably greater than that of the back rolls 1, 1' and the distance between them being in excess of the maximum staple fiber length. Drafting control aprons 6 and 6' are located between these pairs of pinch rolls and forward the fiber bundle intact. The drafting control aprons passing over rolls 4, 4', are located as close to the input nip 5 of the front rolls as is practical. As in normal drafting systems, the aprons 6 and 6' move at a speed slightly in excess of that of the back rolls 1, 1'. The aprons 6, 6 provide an even delivery of fiber to the nip 5 of the front rolls. With the introduction to the system of larger front rolls together with the idler rolls 8, 8' and intake aprons 9, 9, it is possible to draft sliver at yds./min. and above and still obtain uniform drafted sliver.

The presence of the pair of intake aprons or belts 9, 9' around each of the front rolls 2, 2 and around the associated idler rolls 8, 8' in effect extends the nip 5 backward to within a fraction of an inch of the forward end of the drafting control aprons 6, 6'. This gap has been found to be reducible to as little as 0.01 to 0.10

inch. In addition, the direction of the air currents is also changed by this mechanism to the extent that they do not operate with maximum elfect at the intake of the aprons, and disruption of the sliver in its passage is all but eliminated.

The front drafting rolls 2, 2 are driven and are loaded as in conventional drafting systems. The relatively smaller idler rolls 8, 8' are not loaded, being driven only by their contact with the intake aprons. These idler rolls are generally made of steel and contain suitable precision bearings for operation at high speeds since, being aproned to the front rolls 2, 2, they must rotate at. the same surface speed as the front rolls.

In an exemplary drafting system for drafting 20 grains/yd. sliver composed of 1.5 d.p.f. polyacrylonitrile fiber, with an average staple fiber length of 5 inches produced from tow broken on a Turbo-Stapler and pin drafted, the following system would be employed:

The relative surface speeds described above are as follows:

of the drafting elements Yds./min. Back rolls 1, 1' 1.5

Drafting control mil s ZITIIIII:III: 2 Idler rolls 8, 8' 210 Front rolls 2, 2' 210 The front rolls 2, 2 in the new drafting system are conventional in all respects except for their unusually large diameter; that is, they are made of steel cores with the top roll surface covered with the conventional hard rubber/cork composition, and with the bottom roll of steel. Of course, as used in the present invention, these front rolls now contact the sliver by means of the aproned surface rather than the two roll surfaces. The intake aprons 9, 9' are made of a sufficient width to just cover the face of the top front roll, and the two idler rolls 8, 8 are flanged in line with the top roll face to a height equal to the apron thickness, normally 0.0570.067 inch, in order to hold the intake aprons on the front roll faces. These intake aprons 9, 9' are made of the same material as the drafting control aprons, which is normally a flexible laminated rubber composition.

One of the chief advantages of this invention is to provide a simple modification in existing drafting systems to permit drafting sliver and spinning yarn at much higher speeds without affecting the uniformity of the resulting sliver or yarn. The modified apparatus of this invention permits the manufacture of drafted sliver or yarn, at 3 to 10 times the speeds available in the past and still produce products of satisfactory uniformity.

The present invention provides uniform drafted sliver or roving for making spun yarns or core spun yarns which in turn are useful for a wide variety of woven, knitted and nonwoven fabrics useful in a variety of apparel and industrial textile applications. The staple fibers useful for processing and drafting at higher speeds in accordance with this invention include not only natural fibers, such as cotton and wool, but also synthetic fibers, such as those made from polyamides, polyesters, acrylic polymers and copolymers, vinyl polymers and copolymers, polyurethanes, olefin polymers and copolymers, cellulose derivatives such as cellulose acetate, regenerated cellulose, and the like. Blends of two or more natural fibers, two or more synthetic fibers, or blends of natural and synthetic fibers may also be drafted according to the improvements provided by this invention.

What is claimed is:

In a sliver drafting apparatus including a pair of loaded back rolls for metering the input of sliver, and in sequence, drafting control aprons and a pair of loaded front rolls for drafting the sliver, the improvement comprising in combination, front rolls having a diameter that is at least 30% greater than the diameter of the back rolls, and a pair of substantially unloaded idler rolls located between the front rolls and the drafting control aprons, and a set of intake aprons, each passing over an idler roll and a front roll, for removing fibers from the sliver at high speeds in an orderly manner conducive to a uniform drafted product.

References Cited UNITED STATES PATENTS 8/1937 Foster 5736 9/1965 Lohrke 5736 

